It is going to feel strange. Manchester United suddenly seem a lot more vulnerable than they have been for a long time and you wonder what words Sir Alex Ferguson will find to suit the occasion. One more game at Old Trafford, one last bow in front of the old Stretford End and then that moment when he takes the microphone and it is difficult to imagine how he can possibly sum up all the different, clattering emotions.

Will his voice crack? More likely, he will just stick to his lines, thank all the relevant people and keep it relatively brief. A few words about Lady Cathy, inevitably. No doubt he will remember some of the great players and a special mention, perhaps, for Paul Scholes now he is retiring, too.

He might even make a rare appearance in the press room for one last spot of verbal jousting with the people he once chastised for asking whether he could do another three years. That was 2007. "I'll be in my wheelchair," he told us. "You'll be pushing me up the hill so I can have a game of darts at the British Legion."

On Monday there will be one last victory parade. The player of the year dinner is Wednesday and then a trip to West Bromwich Albion next Sunday, bowing out on his 1,500th game when we all know he would rather have made it an odd number at Wembley in a couple of weeks. And then it's simple: he needs to back off.

That is not intended to sound at all mean-spirited or discourteous but if David Moyes is to stand any chance of asserting full authority the lines cannot blur between Ferguson's new boardroom role and the position that has been his way of life for more than a quarter of a century.

Moyes must be allowed to manage the club his way. If he thinks they should give up on the disaffected Wayne Rooney, it must be his decision. If there are players he wants to sign, the club must trust him. If he wants to bring in his own backroom staff it should be ticked off, just as it would at any other major club. If he wants to change some of the working practices at Old Trafford, there should be no need for a second opinion.

It might mean letting someone go, or treading on the toes of someone Ferguson regards as a loyal member of staff. There might be a player Moyes does not rate in the same way that his predecessor did. He might want to remove the barriers that Ferguson has erected between the club and the journalists he keeps offering to send up to Loch Lomond (but only when the midges are out). Or any number of other changes. The bottom line is that, from 1 July, this will be Moyes's club and Ferguson has to let him get on with it. The job is immense enough without any measure of interference.

Norman Whiteside can remember Ferguson being taken aback by the size of the club when he came down from Aberdeen in 1986. "He was in awe of the place. I mean, it was massive. He would come up in training and say to me and Robbo: 'Big place, this, isn't it? Big club, this." Yet the modern United is on a very different scale to the club Ferguson inherited and, in that regard, Moyes should make the most of him being around for advice and conversation, in the same way that Sir Matt Busby was for the younger Ferguson.

That, however, has to be it. Ferguson, as an avid reader of United's history, will not require anyone to recite what happened when Busby could not make a clean break, the problems it created for his successors, Wilf McGuinness and then Frank O'Farrell, and what it says about the importance of United not falling into the same trap.

McGuinness was 31, the same age as Michael Carrick now, when he took over in 1969 and, by his own admission, he struggled to win over the players. Mostly because he was not Busby. He left out Bobby Charlton and Denis Law in a defeat at Everton and soon afterwards the club secretary, Les Olive, discreetly asked him whether he was in close enough contact with Busby. McGuinness will tell you now his suspicion is that Busby initiated that conversation. Stories reached him of Alex Stepney, Willie Morgan and Paddy Crerand going behind his back to complain to the former manager. Michael Parkinson, writing in the Sunday Times, quoted an unnamed player saying that Busby's successor could be given £1m to spend but would still make a mess of it. The transfer record at that time was £165,000.

O'Farrell also dropped Charlton, for a home defeat against Spurs in 1972, and had to go through the jarring experience of Busby telling him he was wrong. Busby started finding fault with Martin Buchan, one of the new manager's signings. O'Farrell's book, All Change At Old Trafford, recalls being undermined more times than he can remember. "Matt questioned my decisions and created discontent. He wasn't the manager but he couldn't let go and became a real hindrance."

Can Ferguson let go? Hypothetical, perhaps, but what happens, say, if six months from now Moyes decides Ryan Giggs's legs are not up to it when Ferguson believes the club's longest‑serving player can carry on for another two seasons?

Maybe the comparison with Busby, more than 40 years later, is too simplistic and unfair on Ferguson to question whether he is capable of keeping his distance. Moyes is no McGuinness. He brings presence and strength of personality and that Ferguson has handpicked him should sway the thinking in the dressing room.

It has also been intriguing to learn over the past few days that some of United's players were not as taken by the possibility of working for José Mourinho as might have been presumed, citing his habit of creating divisions and as one example the way he has marginalised, then ostracised, Iker Casillas at Real Madrid. A bit rich, you might say, bearing in mind Ferguson's own list of fall-outs, but interesting all the same.

Moyes is still coming into the job, however, as someone who has never worked at a club with United's constellation of stars, or even close. His one top-four finish was achieved, remarkably, with a goal difference of minus-one and, though plainly a manager of some distinction, it is a daunting proposition when the last man in the job left a statue as his calling card and accumulated so many trophies MUTV used to have an advert in the club programme showing an old skip outside the stadium overflowing with empty tins of silver polish.

Daniel Rolland lasted one season at Auxerre after Guy Roux, in charge for the previous 36 years, moved aside. Steve Holland was the same after Dario Gradi's 24-year run at Crewe. McGuinness and O'Farrell had 18 months. Joe Kinnear, seventh in line after Brian Clough at Nottingham Forest, grew so sick of hearing about the good times he ended up taking down all the photos of their European nights. "All I ever got was the history of the club rammed down my throat. I couldn't fart without someone bringing up the European Cups."

It is not easy replacing someone who can accurately be described as a legend – one of the most over-used words in sport – and Moyes is going to have to be thick-skinned. He must get used to the sniping, after every disappointment, that he is not a patch on the last manager. Every win, every memorable achievement and every European campaign will be placed in context against his predecessor.

Even the fact Ferguson intends to watch matches from the directors' box brings its own complications. There will be cameras on Ferguson for every second of every match. If the result is poor, you can bet your mortgage there will be photographs or Match of the Day footage of him looking grim-faced over Moyes's left shoulder. Moyes will be asked in press conferences what Ferguson has made of it. If the football is not of butterfly‑beauty, the great Ferguson teams will be cited.

After everything that Ferguson has done, no one can question his right to one of the comfiest seats in the house. Yet when the goodbyes are done, it boils down to this: Moyes becomes the most important man at the club. For his sake, there can be nothing half-hearted about Ferguson's retreat.

Solipsistic Rooney should remember this is not his party

Will Wayne Rooney play any part in Sir Alex Ferguson's final Manchester United game at Old Trafford? Ferguson has continued to involve him since the player's latest transfer request but, now it has been made public, Rooney's appearance against Swansea City would feel incongruous, to say the least, when the memories are still vivid of the crowd's spiteful reaction the last time he tried to leave the club.

Two things come to mind here. The first is that Rooney is hardly in a position to play the aggrieved party given his own record as a bastion of truth and, specifically, the number of times he has gone through the pretence of saying there is nothing in the stories about his future. The second is that he badly misinterprets the mood if he thinks his Twitter bio is a source of great interest at one of the most important times in the club's history.